Method of electric welding



(No Model.)

E. THOMSON.

METHOD 0F ELECTRIC WELDING.

No. 444,927. P atente d J an. 20, 1 89 l FIGLI.-

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UNITED STATES PATENT OFFICE.

ELIHU THOMSON, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE THOMSON ELECTRIC lVEL'DlNG COMPANY, OF MAINE.

METHOD OF ELECTRIC WELDING.V

SPECIFICATION forming part of Letters Patent No. 444,927', dated January 20, 1891.

Application filed May l5, 1888. Serial No. 273.936. (No model.)

.to @ZZ whom it may concern.-

Bc it known that I, ELHU THOMSON, a citizen of the United States, and a resident of Lynn, in the county of Essex and State of Massachusetts, have invented a certain new and useful Method of Electric Velding, of which the t'ollowing is a specification.

My invention relates to those processes ot' electric Welding', bracing, soldering, forging, rbc., in which electric currents of large volume are used as the heating medium, as described in myprior United States patents,Nos. 31E/,140, 7,141, and 347,142, and in my British patent, No. 10,2il of 1886.

My present invention relates to the manner of regulating or graduating the heating-current in the operation; and it consists, essentially, in applying at the beginning et the operation a current of large volume or heating etect, and then as the operation progresses gradually and by small degrees diminishing such current from the beginning, the diminution being, however, so restricted or governed as not to prevent the accumulation of heatin the objects and a rise of temperature to the degree required for effecting the operation. By this means overheating of the Work is eii'ectuallyguarded against, and at the same time the object may be very slowly heated.

My invention consists, also, in cooling the work by gradually decreasing the electric current, while the Work is exposed to a cooling medium, such as the surrounding air or the adjacent clamps or other objects. The fact that the current can be gradually diminished and the progressive heating still take place is owing to the fact that during heating the resistance increases and with each increase ot resistance a less current is required for a given production ot heat. Care must be taken in the operation not to decrease the current too rapidly, since the object would be then cooled, instead of gradually heating.

In practicing myinvention any desired apparatus may be employed and the current may be graduated or controlled by any of the means known in the art-as, for instance, by varying the magnetic eld ot the dynamomachine which gives the current energy, by varying the resistance interposed in the circuit ot` the Welding-currents, by varying the resistance or the inductive resistance in either the primary or secondary of the inductioncoil or converter when the converter is used for developing the Welding-current of large volume, by varying the react-ion or selt`induc tion of the armature or welding circuit when alternating currents derived directly from a dynamo-machine are employed, by varying the inductive relation et the primary and secondary of the converter through changes in their relative position or in the mass or position ot the mass of iron ot' the converter, by varying the speed of the dynamo from which the current is directly or indirectly derived, by varying the position of the comm u tator of the dynamo, or by any other desired means.

Figure l. is a diagram of an apparatus that maybe used in practicing' my invention. Fig. 2 illustrates diagrannnaticallya moditication in the means for varying current. Figs. 3 to l0, inclusive, are graphical representations ot' some of the relations ot current and heating.

Referring to Fig. l, is the secondary, 2 the iron core, and l the primary, of any alter hating-current transformer adapt-ed to convert alternating electric currents into currents ot' greater volume, but loW electro-md tive force, suitable for heating a piece or pieces ot metal held between suitable clamps or holders connected to the terminals of the secondary, as new Well understood in the art. One of the holders may be provided with a means for moving it toward the other, as usual in electric welding operations.

In Fig. l the circuit of the primaryincludes as a means for varying the resistance a reactive coil 4, the reaction of which may be varied by the depth of insertion of an iron core 5, which is carried by a lever pivoted at 7 and provided with a handle G. The handle may be moved over a scale, as indicated, which scale is shown as shaded to represent, when the metal is moved in the direction of the arrow, a current gradually decreasing in strength. The most heavily-shaded part rep- IOO duced by varying the number of turns or lengths ot' an artificial electric resistance. (Indicated at 8, Fig. 2.)

In the diagrams, Figs. 3, 4, 5, and 6, the distance of any point on the heavy black line in a horizontal direction Jfrom zero indicates the strength of current at any given time and the distance of such point in a vertical direction from zero indicates the tem- Io perature, as shown by the Words current and temperature, respectively. Fig. 3 illustrates a condition in which large current is applied and gradually decreased to zero, While the temperature increases, on account of the increase of resistance ot" the metal operated upon when heated. In Figs. 4 and 5 the current is gradually decreased, but not to zero, the temperature and current. remaining about stationary as the desired point is reached for zo metal working. In Fig. 5 a relation is indicated where the current is decreased as the temperature rises and both current and temperature are made to fall toward the finish,

a reaction which is desirable in some opera- 2 5 tions performed upon iron or steel.

Figs. 7, 8, 9, and 10 illustrate graphically the conditions of temperature and current in a dierent manner, the heavily-shaded curve indicating the current and the unshaded curve the temperature, the amount ot current or tem perature being represented 'by the'distance above the horizontal line and the time by the distance in a horizontal direction from the start. In Fig. 7 a relation isillustrated Where the current is gradually-'decreased at ii1'st,the'temperature meantime rising, and toward the finish the current is kept about constant and the temperature remains about the same. In Fig. 8 the current decreases from the start and the tem- 4o perature first rises and then falls. In Fig. 9 the current is made to decrease from start to finish and the temperature rises to the end. Fig. 10 illustrates a condition Where the current is decreased very gradually at the beginning and toward the finish is decreased more rapidly, While the 'temperature rises gradually to a point near the finish, at Which time it is kept about constant by the diminution of the current. 5o

I do not herein claim, broadly, gradually diminishing the current for the purpose of graduating or regulating the heating, as this is claimed, broadly, in another application for patent, tiled of even date herewith, Serial No. 273.985.

That I claim as my invention is- 1. The herein-described improvement in methods of electric Welding, &c., which consists in applying at the start a current of 6o large volume to the Work and gradually diminishing the current from the beginning as l the Work heats.

2. In electric Welding oroth er electric Working of metals, the method of cooling or restoring the Work to normal temperature, consisting in gradually diminishing the heatingcurrent while the work is exposed to a cooling medium.

Signed at Lynn, in the county of Essex and 7o State of Massachusetts, this 11th day of May, A. D. 1888.

ELIHU THOMSON.

IVitnesses:

J. W. GIBBONEY, F. R. HILL. 

